Could a refinery by-product help pave the way to more sustainable roads?

Turning waste material into roads sounds like a win for sustainability, but there may be more to the story.

 

Sulfur could partially replace petroleum-based bitumen in asphalt, potentially lowering costs, reducing reliance on fossil fuels, and giving a productive new use to a surplus refinery by-product. A review by scholars at Arizona State University, however, argues that the road to sustainability requires looking beyond what goes into asphalt, and at what comes out.

 

The study was published in Environmental Chemistry and Safety on Aug. 10.

 

In 2020, the International Maritime Organization tightened global limits on sulfur in marine fuel to better control ship emissions. Sulfur oxides from ship exhaust have been known to exacerbate acid rain, respiratory illness in coastal populations, and environmental degradation.

 

The restrictions prompted petroleum refineries to remove more sulfur from fuels, resulting in a growing surplus of elemental sulfur. Researchers are therefore exploring ways to put it to work in high-volume infrastructure materials such as asphalt.

 

“Sulfur-modified asphalt is a promising approach because it can reduce dependence on petroleum-based binders and provide a beneficial use for refinery sulfur,” said Elham H. Fini, professor at Arizona State University’s School of Sustainable Engineering and the Built Environment and lead author of the study.

 

But it begs the question: is this alternative a greener option, or just a new black one?

 

“Our goal was to look beyond the performance of sulfur-modified asphalt and examine the bigger picture, including potential emissions, exposure pathways, and possible impacts on workers and communities that interact with these materials,” Fini said.

 

To examine these issues, the researchers reviewed literature published from 2000 to 2026 on sulfur-modified asphalt, emissions, environmental exposure and potential health implications.

 

“Sulfur can help reduce costs, improve certain asphalt properties, and support a more circular approach to resource use,” Fini said.

 

But turning sulfur into roads may also change what comes out of those roads.

 

Asphalt can release various substances during binder production, transportation, paving, and other phases throughout its service life. These emissions can create exposure pathways for construction workers and communities living near roads.

 

The authors identify three major gaps in current scholarship: how sulfur chemistry changes asphalt emissions and the formation of sulfur-containing volatile organic compounds; the effects of prolonged human exposure, particularly potential neurological and respiratory impacts; and how emissions change as sulfur-containing asphalt undergoes heating, ultraviolet radiation, oxidation and long-term aging.

 

“Using refinery sulfur in asphalt has great potential, but sustainability is not only about finding a use for a waste material,” Fini said. “We also have to ensure the material is safe throughout its entire life cycle.”

 

The team sees these gaps as opportunities to develop safer materials. Possible approaches include sulfur stabilization through inverse vulcanization and sulfur-based polymers, reduction of volatile emissions with use of bio-derived additives and functional carbon materials, and a more comprehensive evaluation of health risks.

 

Combining materials engineering with environmental and occupational health considerations, the review could assist with the design of future asphalt technologies that provide long-lasting roads while protecting the people who produce, construct and live around them.

 

“Our ultimate goal is to help create next-generation asphalt materials that are not only durable and cost-effective, but also environmentally responsible and safe for workers and communitie. Using refinery sulfur in asphalt has great potential, but sustainability is not only about finding a use for a waste material,”  Fini said. “We also have to ensure the material is safe throughout its entire life cycle.”

 

DOI Link:

https://doi.org/10.26599/ECS.2026.9600056

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